Conventional thermal insulation is characterized by a notable deterioration in its ability to resist heat transfer as the temperature increases. Consequently, the insulating properties ("R factor") are significantly reduced at relatively high mean temperatures. Another problem with many types of insulation is that the density is high and the material is too heavy to be practical for use in many applications. Conventional insulating materials are also subject to degradation when exposed to moisture. There are also limitations as to the ways in which the insulating materials can be applied. For example, conventional materials are not flexible enough to allow their application by spraying, pumping, pouring, or molding, and this further limits the applications in which they can be used.
Although various types of lightweight polymers have been available in recent years, they have for the most part not been useful to construct thermal insulating materials, particularly materials that are used at higher temperatures. The problem is that these polymers tend to have a relatively low melting temperature and can melt if the temperature increases beyond their melting temperature. Thus, while their low density and good insulating properties make many modern materials acceptable in low temperature applications, the fact that they melt at low temperatures renders them useless as high temperature insulation which is exposed to temperatures in excess of about 180.degree. F.